A: Medications, including antacids and antibiotics, can decrease absorption of the pill; and other medications, including anti-seizure drugs and steroids, can cause it to metabolize more quickly. Both can cause breakthrough bleeding.

In some cases, the level of progesterone or estrogen in the body can cause the breakthrough bleeding. Different pills have different levels of hormones in them.

Q: When should I move my toddler from an infant pain reliever to a children í s pain reliever?

A: Acetaminophen is changing to only one concentration: 160 mg/5 ml. Until this change is complete, you will need to pay attention to the concentration you use. Once a child can chew a pill, you might want to change to the chewable form, but read the label and base dosing on weight, not age.

The other common pain reliever used is ibuprofen, which comes in a concentrated infant formulation, a childrenís liquid (usually for children 2 or older) and chewable pills. Ibuprofen is not approved for use in children younger than 6 months. You should follow the package dosage, based on weight, not age.